System and method for monitoring ablation size

ABSTRACT

A system for monitoring ablation size is provided and includes a power source including a microprocessor for executing at least one control algorithm. A microwave antenna is configured to deliver microwave energy from the power source to tissue to form an ablation zone. A radiation detection device is operably disposed on the microwave antenna. The radiation detection device is configured to generate a voltage corresponding to a radius of the ablation zone, wherein the radiation detection device is in operative communication with at least one module associated with the power source. The at least one module triggers a signal when a predetermined threshold voltage is measured corresponding to the radius of the ablation zone.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 12/607,221 filed by Brannan on Oct. 28, 2009, theentire contents of which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to systems and methods that may be usedin tissue ablation procedures. More particularly, the present disclosurerelates to systems and methods for monitoring ablation size duringtissue ablation procedures in real-time.

2. Background of Related Art

In the treatment of diseases such as cancer, certain types of cancercells have been found to denature at elevated temperatures (which areslightly lower than temperatures normally injurious to healthy cells).These types of treatments, known generally as hyperthermia therapy,typically utilize electromagnetic radiation to heat diseased cells totemperatures above 41° C. while maintaining adjacent healthy cells atlower temperatures where irreversible cell destruction will not occur.Procedures utilizing electromagnetic radiation to heat tissue mayinclude ablation of the tissue.

Microwave ablation procedures, e.g., such as those performed formenorrhagia, are typically done to ablate the targeted tissue todenature or kill the tissue. Many procedures and types of devicesutilizing electromagnetic radiation therapy are known in the art. Suchmicrowave therapy is typically used in the treatment of tissue andorgans such as the prostate, heart, and liver.

One non-invasive procedure generally involves the treatment of tissue(e.g., a tumor) underlying the skin via the use of microwave energy. Themicrowave energy is able to non-invasively penetrate the skin to reachthe underlying tissue. However, this non-invasive procedure may resultin the unwanted heating of healthy tissue. Thus, the non-invasive use ofmicrowave energy requires a great deal of control.

Currently, there are several types of systems and methods for monitoringablation zone size. In certain instances, one or more types of sensors(or other suitable devices) are operably associated with the microwaveablation device. For example, in a microwave ablation device thatincludes a monopole antenna configuration, an elongated microwaveconductor may be in operative communication with a sensor exposed at anend of the microwave conductor. This type of sensor is sometimessurrounded by a dielectric sleeve.

Typically, the foregoing types of sensor(s) are configured to function(e.g., provide feedback to a controller for controlling the power outputof a power source) when the microwave ablation device is inactive, i.e.,not radiating. That is, the foregoing sensors do not function inreal-time. Typically, the power source is powered off (or pulsed off)when the sensors are providing feedback (e.g., tissue temperature) tothe controller and/or other device(s) configured to control the powersource.

SUMMARY

The present disclosure provides a system for monitoring ablation size inreal-time. The system includes a power source including a microprocessorfor executing at least one control algorithm. The system includes amicrowave antenna configured to deliver microwave energy from the powersource to tissue forming an ablation zone. A radiation detection deviceis operably disposed on the microwave antenna. The radiation detectiondevice configured to generate a voltage corresponding to a radius of theablation zone. The radiation detection device is in operativecommunication with at least one module associated with the power source,wherein the at least one module triggers a signal when a predeterminedthreshold voltage is measured corresponding to the radius of theablation zone.

The present disclosure provides a microwave antenna adapted to connectto a power source configured for performing an ablation procedure. Themicrowave antenna includes a radiating section configured to delivermicrowave energy from the power source to tissue to form an ablationzone. A radiation detection device is operably disposed on the microwaveantenna. The radiation detection device configured to generate a voltagecorresponding to a radius of the ablation zone. The radiation detectiondevice is in operative communication with one or more modules associatedwith the power source, wherein the at least one module triggers a signalwhen a predetermined threshold voltage is measured corresponding to theradius of the ablation zone.

In one particular embodiment, the one or more modules include anablation zone control module is in operative communication with a memoryassociated with the power source. The memory includes one or more datalook-up tables including rectified dc voltages associated with themicrowave antenna. The rectified dc voltages correspond to a radius ofthe ablation zone. The ablation control module is configured to instructthe power source to adjust the amount of microwave energy beingdelivered to the microwave antenna when a signal from radiationdetection device is received at the ablation zone control module tocreate a uniform ablation zone of suitable proportion with minimaldamage to adjacent tissue.

In an embodiment, a portion of the radiation detection device isoperably positioned at a distal end of a handle associated with themicrowave antenna and extends within an internal portion of a shaftassociated with the microwave antenna.

In an embodiment, the ablation zone control module and radiationdetection device are activated when the power source is activated.Alternatively, the ablation zone control module and radiation detectiondevice are activated when the power source is deactivated. In anembodiment, the radiation detection device includes a resonator inelectrical communication with a resonator coaxial feed extendingdistally along a length of the shaft. A distal end of the resonatorcoaxial feed is positioned adjacent a radiating section of the microwaveantenna and is configured to detect radiation during the delivery ofmicrowave energy from the power source to tissue and induce anelectromagnetic field within the resonator such that a rectified dcvoltage is generated at the resonator and communicated to the ablationzone control module. The resonator coaxial feed may be made from a metalselected from the group consisting of copper, silver and gold. In oneparticular embodiment, the resonator is a substantially enclosedstructure for resonating an electromagnetic field within the resonator.The resonator may be generally cylindrical and made from a metalselected from the group consisting of copper, silver and gold.

In an embodiment, the resonator includes a generally circumferential gapdividing the resonator into two conductive portions in electricalcommunication with one another and electrically isolated from oneanother. The two conductive portions are in electrical communicationwith the ablation zone control module via a pair of conductive leads.One or more diodes extend across the gap and operably couples to each ofthe two conductive portions of the resonator. The one or more diodes isconfigured to produce a rectified dc voltage that corresponds to theelectromagnetic field within the resonator.

In an embodiment, a dielectric coating may be disposed between the shaftand the resonator coaxial feed to prevent electrical shorting betweenthe resonator coaxial feed and the shaft.

In an embodiment, the microwave antenna may be configured to produce anablation zone that is spherical.

In an embodiment, the microwave antenna may be configured to produce anablation zone that is ellipsoidal.

The present disclosure also provides a method for monitoring temperatureof tissue undergoing ablation. The method includes an initial step oftransmitting microwave energy from a power source to a microwave antennato form a tissue ablation zone. A step of the method includes monitoringcomplex impedance associated with the microwave antenna as the tissueablation zone forms. A step of the method includes communicating acontrol signal to the power source when a predetermined rectified dcvoltage is reached at the microwave antenna. Adjusting the amount ofmicrowave energy from the power source to the microwave antenna isanother step of the method.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentdisclosure will become more apparent in light of the following detaileddescription when taken in conjunction with the accompanying drawings inwhich:

FIG. 1A is a perspective view of a system for monitoring ablation sizeaccording to an embodiment of the present disclosure;

FIG. 1B is a perspective view of a system for monitoring ablation sizeaccording to another embodiment of the present disclosure;

FIG. 2A is partial cut-away view of a distal tip of a microwave antennadepicted in FIG. 1A;

FIG. 2A-1 is a cross-section view taken along line segment 2A-1 of FIG.2A;

FIG. 3A is a schematic, plan view of the tip of a microwave antennadepicted in FIG. 2A illustrating radial ablation zones associated withthe microwave antenna during activation and having a sphericalconfiguration;

FIG. 3B is a graphical representation of a rectified dc voltage (Vdc)versus time (t) curve;

FIG. 3C is a schematic, plan view of the tip of a microwave antennadepicted in FIG. 2A illustrating radial ablation zones associated withthe microwave antenna during activation and having an ellipsoidalconfiguration;

FIG. 4 is a functional block diagram of a power source for use with thesystem depicted in FIG. 1A;

FIG. 5 is a flow chart illustrating a method for monitoring temperatureof tissue undergoing ablation in accordance with the present disclosure;and

FIG. 6 is partial cut-away view of a distal tip of a microwave antennaaccording to an alternate embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the presently disclosed system and method are describedin detail with reference to the drawing figures wherein like referencenumerals identify similar or identical elements. As used herein and asis traditional, the term “distal” refers to a portion that is furthestfrom the user and the term “proximal” refers to a portion of themicrowave antenna that is closest to the user. In addition, terms suchas “above,” “below,” “forward,” “rearward,” etc. refer to theorientation of the figures or the direction of components and are simplyused for convenience of description.

Referring now to FIG. 1A, a system for monitoring ablation size inaccordance with an embodiment of the present disclosure is designated10. The system 10 includes a microwave antenna 100 that is adapted toconnect to an electrosurgical power source, e.g., an RF and/or microwave(MW) generator 200 that includes or is in operative communication withone or more controllers 300 and, in some instances, a fluid supply pump40. Briefly, microwave antenna 100 includes an introducer 116 having anelongated shaft 112 and a radiating or conductive section or tip 114operably disposed within elongated shaft 112, a cooling assembly 120having a cooling sheath 121, a handle 118, a cooling fluid supply 122and a cooling fluid return 124, and an electrosurgical energy connector126. Connector 126 is configured to connect the microwave antenna 100 tothe electrosurgical power source 200, e.g., a generator or source ofradio frequency energy and/or microwave energy, and supplieselectrosurgical energy to the distal portion of the microwave antenna100. Conductive tip 114 and elongated shaft 112 are in electricalcommunication with connector 126 via an internal coaxial cable 126 athat extends from the proximal end of the microwave antenna 100 andincludes an inner conductor tip that is operatively coupled to aradiating section 138 operably disposed within the shaft 112 andadjacent the conductive or radiating tip 114 (see FIG. 2A, for example).As is common in the art, internal coaxial cable 126 a is includes adielectric material and an outer conductor surrounding each of the innerconductor tip and dielectric material. A connection hub (not shown)disposed at a proximal end of the microwave antenna 100 operably couplesconnector 126 to internal coaxial cable 126 a, and cooling fluid supply122 and a cooling fluid return 124 to a cooling assembly 120. Radiatingsection 138 by way of conductive tip 114 (or in certain instanceswithout conductive tip 114) is configured to deliver radio frequencyenergy (in either a bipolar or monopolar mode) or microwave energy to atarget tissue site. Elongated shaft 112 and conductive tip 114 may beformed of suitable conductive material including, but not limited tocopper, gold, silver or other conductive metals having similarconductivity values. Alternatively, elongated shaft 112 and/orconductive tip 114 may be constructed from stainless steel or may beplated with other materials, e.g., other conductive materials, such asgold or silver, to improve certain properties, e.g., to improveconductivity, decrease energy loss, etc. In an embodiment, theconductive tip may be deployable from the elongated shaft 112.

In an alternate embodiment, system 10 may be configured for use with amicrowave antenna 512 illustrated in FIG. 1A. Briefly, microwave antenna512 is coupled to a generator 200 including a controller 300 via aflexible coaxial cable 516. In this instance, generator 200 isconfigured to provide microwave energy at an operational frequency fromabout 500 MHz to about 10 GHz. Microwave antenna 512 includes aradiating portion 518 that may be connected by feedline 20 (or shaft) tothe cable 516. More specifically, the microwave antenna 512 is coupledto the cable 516 through a connection hub 522. The connection hub 522also includes an outlet fluid port 530 (similar to that of cooling fluidreturn 124) and an inlet fluid port 532 (similar to that of coolingfluid supply 122) that are connected in fluid communication with asheath 538. The sheath 538 encloses the radiating portion 518 and thefeedline 520 allowing for coolant fluid from the ports 530 and 532 to besupplied and circulated around the antenna assembly 512. The ports 530and 532 are also coupled to a supply pump 534 (similar to that of fluidsupply pump 40). For a more detailed description of the microwaveantenna 512 and operative components associated therewith, reference ismade to commonly-owned U.S. patent application Ser. No. 12/401,268 filedon Mar. 10, 2009.

For the remainder of the disclosure the operative components associatedwith the system 10 are described with reference to microwave antenna100.

With reference to FIG. 2A, a radiation detection device 130 is inoperative communication with the microwave antenna 100, controller 300,and/or generator 200. Radiation detection device 130 is configured togenerate a rectified dc voltage Vdc that corresponds to a radius “r” ofan ablation zone “A” associated with an ablation procedure. To this end,radiation detection device 130 is in operative communication with one ormore modules (e.g., an ablation zone control module “AZCM 332”)associated with the generator 200. In one particular embodiment, theAZCM 332 triggers a signal when a predetermined rectified dc voltage,e.g., Vdc5, is measured corresponding to the radius “r” of the ablationzone “A” (described in greater detail below).

With continued reference to FIG. 2A, the components of radiationdetection device 130 are now described. Radiation detection device 130includes a resonator portion 132 in electrical communication with aresonator coaxial feed 134. In the embodiment illustrated in FIGS. 1Aand 2A, resonator 132 is operably disposed within an internal portion ofthe handle 118 adjacent the elongated shaft 112. The relatively largevolume of the handle 118 (when compared to other components, e.g., shaft112, associated with the microwave antenna 100) provides a larger volumefor the resonator 132 to be designed within. Moreover, a hub (e.g., ahub similar to hub 522 associated with microwave antenna 512) associatedwith the fluid cooled supply and return lines 122 and 124, respectively,provides a useful dielectric loading (e.g., saline, water, etc.) thatcan be utilized to reduce the size of the resonator 132 for a givenfrequency of operation.

In accordance with the present disclosure, an electromagnetic field isinduced within the resonator 132 and resonates within the resonator 132during an ablation procedure. To this end, resonator 132 is asubstantially enclosed structure having dimensions of suitableproportion. More particularly, a generally circumferential gap “g”essentially divides or separates the resonator 132 into two spaced-apartconductive portions 142 and 144 that are in electrical communicationwith one another and electrically insulated from one another (i.e., toprevent shorting between the conductive portions 142 and 144). Gap “g”provides a location of high voltage potential, e.g., Vdc, between thetwo conductive portions 142 and 144. Gap “g” may have any suitabledimensions. In certain embodiments, the gap “g” may partially divide orseparate the resonator 132. While the embodiment illustrated in FIGS. 1Aand 2A illustrates conductive portions 142 and 144 collectively definingthe resonator 132 with a generally cylindrical configuration, it iswithin the purview of the present disclosure that resonator 132 may haveany suitable configuration, e.g., rectangular, square, etc. One or bothof the conductive portions 142 and 144 operably couples to the radiatingsection 138. More particularly, a distal end 136 of the conductiveportion 144 operably couples to the resonator coaxial feed 134 thatextends distally toward the radiating section 138 along a length of aninternal electrical feed tube 158 that houses the internal cable 126 a(see FIG. 2A, for example). In the embodiment illustrated in FIG. 2A,internal electrical feed tube 158 supports the conductive members 142and 144 and/or resonator coaxial feed 134 in a substantially fixedposition. Alternatively, one or more components (e.g., an internal wallor other suitable structure) associated with the microwave antenna 100may operably couple to the radiation detection device 130, or componentsassociated therewith, e.g., one or both of the conductive portions 142and 144. For example, one or both of the conductive portions 142 and 144of radiation detection device 130 may be secured to an internal frameassociated with the microwave antenna 100. Resonator 132 includingconductive portions 142 and 144 may be made from any suitable material.In the embodiment illustrated in FIG. 2A, resonator 132 includingconductive portions 142 and 144 is made from one or more types of metalhaving conductive properties conducive for inducing an electromagneticfield within the resonator 132, such that the electromagnetic fieldresonates therein for a time sufficient to provide a voltage drop at oracross the gap “g.” More particularly, resonator 132 includingconductive portions 142 and 144 is made from a metal selected from thegroup consisting of copper, silver, gold, stainless steal, chrome andbrass. In one particular embodiment, the conductive portions 142 and 144are each made from copper.

One or more conductive leads operably couple to one or more componentsassociated with the resonator 132 to provide electrical communicationbetween one or more modules, e.g., AZCM 332, of the controller 300and/or generator 200. More particularly, conductive portions 142 and 144are in electrical communication with the AZCM 332 via a respectiveconductive lead 146 and 148. In the embodiment illustrated in FIG. 2A,conductive lead 146 connects to a positive terminal associated with oneor more modules, e.g., AZCM 332, of the generator 300 and/or controller200. Similarly, conductive lead 148 connects to a negative terminalassociated with one or more modules, e.g., AZCM 332, of the generator300 and/or controller 200. Leads 146 and 148 may secure to therespective conductive portions 142 and 144 via any suitable securementmethods known in the relevant art, e.g., solder, electrical contacts orclips, and so forth. The leads 146 and 148 may follow the sameelectrical line feed paths as internal cable 126 a, as best seen in FIG.2A.

One or more diodes 150 (one diode 150 is shown in the representativedrawings) extend across the gap “g” and operably couple to each of thetwo conductive portions 142 and 144 of the resonator 132 such that avoltage drop across the diode 150 may be achieved when anelectromagnetic field is induced within the resonator 132. Diode 150 isconfigured to produce a rectified dc voltage Vdc that corresponds to theresonating electromagnetic field within the resonator 130 at a time “t”(see FIG. 3B, for example). In an embodiment, a plurality of diodes 150(not explicitly shown) may operably couple to the conductive portions142 and 144 and may be configured to function as a full or half waverectifier. Diode 150 may provide additional structural support to thetwo conductive members 142 and 144. That is, the diode 150 mayfacilitate in maintaining the conductive portions 142 and 144 in asubstantially fixed and spaced-apart relation with respect to oneanother. Alternatively, or in combination therewith, one or morenon-conductive members, e.g., non-conductive bridges (not shown), may beprovided at predetermined locations between the two conductive portions142 and 144 and along the gap “g.” More particularly, the non-conductivebridges extend from one conductive portion, e.g., conductive portion142, to the other conductive portion, e.g., conductive portion 144, tomaintain the conductive portions 142 and 144 in a substantially fixedand spaced apart relation with respect to one another. Thenon-conductive bridges may be made from any suitable material, such as,for example, thermal plastics with high melting points.

Resonator coaxial feed 134 is in electrical communication with theresonator 132. More particularly, resonator coaxial feed 134 is inelectrical communication with one or both conductive portions 142 and144. In the embodiment illustrated in FIG. 2A, resonator coaxial feed134 is in electrical communication with conductive portion 144 (as bestseen FIG. 2A). As noted above, resonator coaxial feed 134 extendsdistally from distal end 136 of the conductive member 144 along internalelectrical feed tube 158 toward the radiating section 138. A distal end156 of the resonator coaxial feed 134 is positioned in the generalproximity of radiating section 138 of the microwave antenna 100 andconfigured to detect radiation during the delivery of microwave energyfrom the generator 200 to tissue such that an electromagnetic field isinduced within the resonator 132. Resonator coaxial feed 134 may be madefrom any suitable material (e.g., metal) that is capable of detectingradiation and inducing an electromagnetic field within the resonator132. In one particular embodiment, resonator coaxial feed 134 is madefrom copper. In an alternate embodiment, resonator coaxial feed 134 maybe made from a combination of metals such as, for example, thecombination of metals selected from the group consisting of copper, goldand silver. A dielectric coating 152 is operably disposed between theinternal electrical feed tube 158 and the resonator coaxial feed 134 toprevent electrical shorting between the resonator coaxial feed 134 andthe internal electrical feed tube 158, or operative componentsassociated therewith, e.g., internal cable 126 a and/or radiatingsection 138. In one particular embodiment, the combination of a catheter154 associated with the microwave antenna 100 and one or both of thecooling fluid lines, e.g., cooling fluid supply line 122 and coolingfluid return lines 124, may also serve as a dielectric coating 152. Incertain embodiments, a dielectric coating 152 may be operably disposedbetween the shaft 112 and the resonator coaxial feed 134 to preventelectrical shorting between the resonator coaxial feed 134 and the shaft112 or operative components associated therewith, e.g., conductive tip114.

With reference to FIG. 4, a schematic block diagram of the generator 200is illustrated. The generator 200 includes a controller 300 having oneor more modules (e.g., an ablation zone control module 332 (AZCM 332), apower supply 237 and a microwave output stage 238). In this instance,generator 200 is described with respect to the delivery of microwaveenergy. The power supply 237 provides DC power to the microwave outputstage 238 which then converts the DC power into microwave energy anddelivers the microwave energy to the radiating section 138 of themicrowave antenna 100. The controller 300 may include analog and/orlogic circuitry for processing sensed values provided by the AZCM 332and determining the control signals that are sent to the generator 200and/or supply pump 40 via a microprocessor 335. The controller 300 (orcomponent operably associated therewith) accepts one or more measuredsignals indicative of a rectified dc voltage (e.g., dc voltage Vdcgenerated by the resonator 132 of the radiation detection device)associated with the microwave antenna 100 when the microwave antenna 100is radiating energy.

One or more modules e.g., AZCM 332, of the controller 300 analyzes themeasured signals and determines if a threshold rectified dc voltage(s)Vdc, e.g., Vdc5, corresponding to an ablation zone “A” having acorresponding radius “r”, e.g., radius r5, has been met. If thethreshold rectified dc voltage(s) (e.g., Vdc5) has been met, then theAZCM 332, microprocessor 335 and/or the controller instructs thegenerator 200 to adjust the microwave output stage 238 and/or the powersupply 237 accordingly. Additionally, the controller 300 may also signalthe supply pump to adjust the amount of cooling fluid to the microwaveantenna 100 and/or the surrounding tissue. The controller 200 includesmicroprocessor 335 having memory 336 which may be volatile type memory(e.g., RAM) and/or non-volatile type memory (e.g., flash media, diskmedia, etc.). In the illustrated embodiment, the microprocessor 335 isin operative communication with the power supply 237 and/or microwaveoutput stage 238 allowing the microprocessor 335 to control the outputof the generator 300 according to either open and/or closed control loopschemes. The microprocessor 335 is capable of executing softwareinstructions for processing data received by the AZCM 332, and foroutputting control signals to the generator 300 and/or supply pump 40,accordingly. The software instructions, which are executable by thecontroller 300, are stored in the memory 336.

One or more control algorithms for predicting tissue ablation size isimplemented by the controller 300. More particularly, the concept ofcorrelating a rectified dc voltage (e.g., a rectified dc voltage Vdcgenerated by the resonator 132) associated with a particular microwaveantenna, e.g., the microwave antenna 100, with an ablation zone “A”having a radius “r” may be used to indicate tissue death or necrosis. Arelationship of the generated rectified dc voltage Vdc as a function oftime “t” is illustrated in FIG. 3B. As a microwave ablation cycleprogresses, electromagnetic radiation at a “near field,” e.g., areaadjacent the ablation site, of the microwave antenna 100 varies (e.g.,increases) over the course of the ablation cycle due to tissue complexpermittivity change caused by temperature increase. When the microwaveantenna 100 has heated tissue to a desired temperature, a desiredablation zone “A” having a corresponding radius “r” is (e.g., radiusr1,) is formed and electromagnetic radiation is emitted at the “nearfield.” Resonant coaxial feed 134 of the radiation detection device 130detects the electromagnetic radiation and induces an electromagneticfield within the resonator 132 such that a corresponding dc voltage,e.g., Vdc1, is generated and communicated to the ACZM 332. Moreparticularly, diode 150 produces rectified dc voltages Vdc1-Vdc5 thatcorresponds to the resonating electromagnetic field within the resonator130 at times t1-t5, see FIG. 3B, for example).

It should be noted, that the amount of electromagnetic radiation emittedat the “near field” may vary for a given microwave antenna. Factors thatmay contribute to a specific amount of electromagnetic radiation for agiven microwave antenna include but are not limited to: dimensionsassociated with the microwave antenna (e.g., length, width, etc.); typeof material used to manufacture the microwave antenna (or portionassociated therewith, e.g., a radiating section) such as copper, silver,etc; and the configuration of a conductive tip associated with themicrowave antenna (e.g., sharp, blunt, curved, etc).

The microwave antenna 100 of the present disclosure may be configured tocreate an ablation zone “A” having any suitable configuration, such as,for example, spherical (FIG. 3A), hemispherical, ellipsoidal (FIG. 3Cwhere the ablation zone is designated “A-2”), and so forth. In oneparticular embodiment, microwave antenna 100 is configured to create anablation zone “A” that is spherical (see FIG. 3A, for example). As notedabove, when the microwave antenna 100 has heated tissue in the “nearfield” to a specific temperature, e.g., at time t1, electromagneticradiation is emitted at the “near field” and detected by resonantcoaxial feed 134 such that an electromagnetic radiation is inducedwithin the resonator 132, which, turn generates a correspondingrectified dc voltage, e.g., Vdc1, that is communicated to the ACZM 332.Correlating the rectified dc voltage Vdc associated with the microwaveantenna 100 with the ablated tissue, indicates a specific size (e.g.,radius r1) and shape (e.g., spherical) of the ablation zone “A.” Thus, ameasure of the rectified dc voltage Vdc, e.g., Vdc1 associated with themicrowave antenna 100 corresponds to an ablation zone “A” having aradius “r”, e.g., radius r1. The control algorithm of the presentdisclosure uses known rectified dc voltages, Vdc1-Vdc5 associated withspecific microwave antennas at specific radii to predict an ablationsize. That is, threshold voltages, e.g., Vdc5, associated with aspecific microwave antenna, e.g., microwave antenna 100, andcorresponding radius, e.g., r5, are compiled into one or more look-uptables “D” and are stored in memory, e.g., memory 336, accessible by themicroprocessor 335 and/or the AZCM 332. Thus, when the thresholdrectified dc voltage Vdc for a specific microwave antenna, e.g.,microwave antenna 100, reaches, for example, Vdc5 one or more modules,e.g. AZCM 332, associated with the controller 300, commands thecontroller 200 to adjust the power output to the microwave antenna 100accordingly. This combination of events will provide an ablation zone“A” with a radius approximately equal to r5.

In the illustrated embodiments, for a given microwave antenna, e.g.,microwave antenna 100, voltage measurements are taken at times t1-t5. Inthis instance, voltages, e.g., Vdc1-Vdc5, associated with the microwaveantenna 100 may be correlated with an ablation zone “A” defined by aplurality of concentric ablation zones having radii r1-r5 (collectivelyreferred to as radii r) when measured from the center of the ablationzone “A.” In this instance, when specific dc voltages, e.g., Vdc3, ismet one or more modules, e.g. AZCM 332, associated with the controller300, commands the controller 200 to adjust the power output to themicrowave antenna 100 accordingly.

AZCM 332 may be a separate module from the microprocessor 335, or AZCM332 may be included with the microprocessor 335. In an embodiment, theAZCM 332 may be operably disposed on the microwave antenna 100. The AZCM332 may include control circuitry that receives information from one ormore control modules, and provides the information to the controller 300and/or microprocessor 335. In this instance, the AZCM 332,microprocessor 335 and/or controller 300 may access look-up table “D”and confirm that a threshold rectified dc voltage Vdc (e.g., Vdc5)associated with microwave assembly 100 that corresponds to a specificablation zone, e.g., specific ablation zone having a radius r₅, has beenmet and, subsequently instruct the generator 200 to adjust the amount ofmicrowave energy being delivered to the microwave antenna. In oneparticular embodiment, look-up table “D” may be stored in a memorystorage device (not shown) associated with the microwave antenna 100.More particularly, a look-up table “D” may be stored in a memory storagedevice operatively associated with handle 118 and/or connector 126 ofthe microwave antenna 100 and may be downloaded, read and stored intomicroprocessor 335 and/or memory 336 and, subsequently, accessed andutilized in a manner described above; this would do away withreprogramming the generator 200 and/or controller 300 for a specificmicrowave antenna. The memory storage device may also be configured toinclude information pertaining to the microwave antenna 100. Forexample, information such as, the type of microwave antenna, the type oftissue that the microwave antenna is configured to treat, the type ofablation zone, etc. may be stored into the storage device associatedwith the microwave antenna. In this instance, for example, generator 200and/or controller 300 of system 10 may be adapted for use with amicrowave antenna configured to create an ablation zone, e.g. ablationzone “A-2,” different from that of microwave antenna 100 that isconfigured to create an ablation zone “A.”

In the embodiment illustrated in FIG. 1A, the generator 200 is shownoperably coupled to fluid supply pump 40. The fluid supply pump 40 is,in turn, operably coupled to the supply tank 44. In embodiments, themicroprocessor 335 is in operative communication with the supply pump 40via one or more suitable types of interfaces, e.g., a port 240operatively disposed on the generator 200, that allows themicroprocessor 335 to control the output of a cooling fluid 42 from thesupply pump 40 to the microwave antenna 100 according to either openand/or closed control loop schemes. The controller 300 may signal thesupply pump 40 to control the output of cooling fluid 42 from the supplytank 44 to the microwave antenna 100. In this way, cooling fluid 42 isautomatically circulated to the microwave antenna 100 and back to thesupply pump 40. In certain embodiments, a clinician may manually controlthe supply pump 40 to cause cooling fluid 42 to be expelled from themicrowave antenna 100 into and/or proximate the surrounding tissue.

Operation of system 10 is now described. Initially, microwave antenna100 is connected to generator 200. In one particular embodiment, one ormore modules, e.g., AZCM 332, associated with the generator 200 and/orcontroller 300 reads and/or downloads data from a storage deviceassociated with the microwave antenna 100, e.g., the type of microwaveantenna, the type of tissue that is to be treated, etc. Thereafter,generator 200 may be activated supplying microwave energy to radiatingsection 138 of the microwave antenna 100 such that the tissue may beablated. During tissue ablation, when a predetermined rectified dcvoltage Vdc, e.g., V5, at the resonator 132 of the microwave antenna 100is reached (i.e., a rectified voltage across diode 150 is present), theAZCM 332 instructs the generator 200 to adjust the microwave energyaccordingly. In the foregoing sequence of events the AZCM 332 functionsin real-time controlling the amount of microwave energy to the ablationzone such that a uniform ablation zone of suitable proportion (e.g.,ablation zone “A” having a radius r5) is formed with minimal or nodamage to adjacent tissue.

With reference to FIG. 5 a method 400 for monitoring temperature oftissue undergoing ablation is illustrated. At step 402, microwave energyfrom generator 200 is transmitted to a microwave antenna 100 adjacent atissue ablation site. At step, 404, dc voltage Vdc associated with themicrowave antenna 100 is monitored. At step 406, a detection signal iscommunicated to the generator 200 when a predetermined rectified dcvoltage Vdc is reached at the microwave antenna 100. At step 408, theamount of microwave energy from the generator 200 to the microwaveantenna 100 may be adjusted.

From the foregoing and with reference to the various figure drawings,those skilled in the art will appreciate that certain modifications canalso be made to the present disclosure without departing from the scopeof the same. For example, in an alternate embodiment, radiationdetection device 130 (or operative components associated therewith) maybe operably disposed internally along the shaft 112 adjacent radiatingsection 138 of microwave antenna 100 (FIG. 6) or internally along thefeedline 520 adjacent radiating section 518 of microwave antenna 512. Inthe embodiment illustrated in FIG. 6, the resonator 130 includingconductive members 142 and 144 and coaxial feed 134 are fixedlysupported to catheter 154 via a pair of supports 160. Operation of theradiation detection device 130 and operative components associatedtherewith function in a manner as described above with respect to theradiation detection device 130 being disposed within the handle 118 and,as result thereof, will not be described in further detail.

It is contemplated that one or both of the conductive portions 142 and144 may be coated with an insulative coating or sheathing (not shown)configured to insulate or electrically isolate the conductive portions142 and 144 (or other operative components associated with the resonator132) from one another and/or surrounding components associated with themicrowave antenna 100. More particularly, proximal and distal edges ofthe respective conductive portions 144 and 142 may include an insulativematerial (not explicitly shown) to prevent shorting between theconductive members 142 and 144. Alternatively, or in combinationtherewith, an outer peripheral surface of one or both of the conductiveportions 142 and 144 may be coated or formed from an insulativematerial.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

What is claimed is:
 1. A method for monitoring temperature of tissueundergoing ablation, the method comprising: transmitting microwaveenergy from a power source to a microwave antenna to form a tissueablation zone; monitoring the proximal propagation of tissue temperaturealong the microwave antenna as the tissue ablation zone forms;communicating a detection signal when a predetermined dc voltage isreached within the microwave antenna; and adjusting the amount ofmicrowave energy from the power source to the microwave antenna.
 2. Amethod according to claim 1, including providing the microwave antennawith a radiation detection device that is operably disposed on themicrowave antenna.
 3. A method according to claim 2, further includingpositioning at least a portion of the radiation detection device at adistal end of a handle associated with the microwave antenna andextending the at least a portion of the radiation detection devicewithin an internal portion of a shaft associated with the microwaveantenna.
 4. A method according to claim 2, including utilizing theradiation detection device to generate a voltage corresponding to aradius of the ablation zone, wherein the radiation detection device isin operative communication with at least one module associated with thepower source, wherein the at least one module triggers the detectionsignal when the predetermined dc threshold voltage is measuredcorresponding to the radius of the ablation zone.
 5. A method accordingto claim 2, further including providing an ablation zone control modulethat is in operative communication with a memory associated with thepower source, the memory including at least one data look-up tableincluding rectified dc voltages associated with the microwave antenna,the rectified dc voltages corresponding to a radius of the ablationzone.
 6. A method according to claim 5, including utilizing the ablationcontrol module to instruct the power source to adjust the amount ofmicrowave energy being delivered to the microwave antenna when a signalfrom radiation detection device is received at the ablation zone controlmodule to create a uniform ablation zone of suitable proportion withminimal damage to adjacent tissue.
 7. A method according to claim 5,including activating the ablation control zone module and radiationdetection device when the power source is activated.
 8. A methodaccording to claim 5, including activating the ablation control zonemodule and radiation detection device when the power source isdeactivated.
 9. A method according to claim 5, including providing theradiation detection device with a resonator in electrical communicationwith a resonator coaxial feed extending distally along a length of ashaft of the microwave antenna, a distal end of the resonator coaxialfeed positioned adjacent a radiating section of the microwave antennaand configured to detect radiation during the delivery of microwaveenergy from the power source to tissue and induce an electromagneticfield within the resonator such that a rectified dc voltage is generatedat the resonator and communicated to the ablation zone control module.10. A method according to claim 9, including substantially enclosing theresonator to resonate an electromagnetic field within the resonator. 11.A method according to claim 9, including providing the resonator with agenerally cylindrical configuration.
 12. A method according to claim 9,including forming the resonator from a metal selected from the groupconsisting of copper, silver, gold, stainless steel, chrome and brass.13. A method according to claim 9, including providing a dielectriccoating between the shaft and the resonator coaxial feed to preventelectrical shorting between the resonator coaxial feed and the shaft.14. A method according to claim 9, including forming the resonatorcoaxial feed from a metal selected from the group consisting of copper,silver, gold, stainless steel, chrome and brass.
 15. A method accordingto claim 9, including providing the resonator with a generallycircumferential gap that divides the resonator into two conductiveportions that are in electrical communication with one another andelectrically isolated from one another, the two conductive portions inelectrical communication with the ablation zone control module via apair of conductive leads.
 16. A method according to claim 15, includingproviding at least one diode that extends across the generallycircumferential gap and operably couples to each of the two conductiveportions of the resonator, the at least one diode configured to producea rectified dc voltage that corresponds to the electromagnetic fieldwithin the resonator.
 17. A method according to claim 1, furtherincluding producing an ablation zone that is one of spherical andellipsoidal.
 18. A method according to claim 1, further includingproviding at least one fluid pump that is configured to supply a coolingfluid to the microwave antenna for facilitating cooling of one of themicrowave antenna and tissue adjacent the ablation zone.